Embroidery frame

ABSTRACT

An embroidery frame includes an outer frame formed into a substantially annular shape and having a discontinuity formed by partially breaking its annularity so that the outer frame has two ends located opposite each other with the discontinuity being interposed, an inner frame configured to be fitted with an inner periphery of the outer frame, a clamping mechanism clamping the outer frame against the inner frame and including paired screw-supporting members mounted on the outer frame ends and an adjusting screw mounted on the screw-supporting members so as to adjust a gap between the screw mounting members, and an operating knob supported on an operating end of the screw so as to be switchable between a first position where the knob extends parallel to an axial direction of the screw and a second position where the knob extends in a direction substantially perpendicular to the axial direction.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is based upon and claims the benefit of priority from the prior Japanese Patent Application No. 2010-231505 filed on Oct. 14, 2010, the entire contents of which are incorporated herein by reference.

BACKGROUND

1. Technical Field

The present disclosure relates to an embroidery frame including an outer frame and an inner frame and holding a workpiece cloth between the outer and inner frames.

2. Related Art

Conventional embroidery sewing machines comprise an embroidery frame holding a workpiece cloth and an embroidery frame transfer mechanism transferring the workpiece cloth. In the embroidery sewing machines, a needle bar mechanism and other drive mechanisms are controlled while the embroidery frame is transferred in an X or a right-left direction and in a Y or front-back direction, whereby an embroidery pattern is sewn on the workpiece cloth.

The aforementioned embroidery frame includes an inner frame generally formed into a rounded rectangularly annular shape, an outer frame disposed outside the inner frame and generally formed into a rectangular frame-shape and has a splitting section, and a clamping mechanism which clamps the outer frame against the inner frame. The clamping mechanism comprises a pair of screw-attachment portions provided at both sides of the splitting section of the outer frame respectively and an adjusting screw for connecting the screw-attachment portions together. More specifically, one of the screw-attachment portions or the right screw-attachment portion is provided with an insertion hole through which a part of the adjusting screw is inserted. The other or left screw-attachment portion is provided with a nut with which a middle portion of the adjusting screw is threadingly engaged. When a workpiece cloth is set on the embroidery frame, an operator turns a head of the screw to increase a width between the screw-attachment portions, placing a workpiece cloth between the outer and inner frames. Next, the operator turns the screw head in the opposite direction so that the width between the screw-attachment portions is reduced. Thus, the outer frame is fastened to the inner frame such that the workpiece cloth is held between the outer and inner frames.

An embroidery frame having another clamping mechanism is also known. This embroidery frame is provided with an operating shaft which turns the adjusting screw of the clamping mechanism. The operating shaft is coupled via a coupling mechanism with the adjusting screw. The coupling mechanism couples the operating shaft with the adjusting screw so that the adjusting screw is swingable. When a workpiece cloth is set on the embroidery frame, the operator swings or moves the operating shaft so that the operating shaft is located at a position where the operator can easily operate the operating shaft. Thereafter, the operator turns an operating portion at a distal end of the operating shaft with his/her fingertips, whereupon the adjusting screw can be turned.

In the above-described fastening mechanism, the adjusting screw head or the operating portion of the operating shaft has a relatively smaller outer diameter. Accordingly, some operators have a difficulty in turning the adjusting screw or the operating shaft with a sufficiently large force with the result that the outer frame cannot be fastened tightly to the inner frame. In view of this problem, it is considered to increase the outer diameter of the adjusting screw head or the operating portion of the operating shaft. However, when the outer diameter of the adjusting screw head or the operating portion of the operating shaft is increased, the adjusting screw head or the operating portion would contact a sewing machine bed during a sewing operation of the embroidery sewing machine. This would result in malfunction in transferring the embroidery frame.

SUMMARY

Therefore, an object of the disclosure is to an embroidery frame provided with an operating knob which turns the adjusting screw of the fastening mechanism fastening the outer frame to the inner frame and which can easily be turned with a smaller operating force and can tightly fasten the outer frame to the inner frame.

The present disclosure provides an embroidery frame which holds a workpiece cloth, comprising an outer frame formed into a substantially annular shape and having a discontinuity formed by partially breaking the annularity of the outer frame so that the outer frame has two ends located opposite each other with the discontinuity being interposed therebetween, an inner frame configured to be fitted with an inner periphery of the outer frame so that the workpiece cloth is held between the outer and inner frames, a clamping mechanism which clamps the outer frame against the inner frame and includes a pair of screw-supporting members provided on the ends of the outer frame respectively and an adjusting screw which is mounted on the screw-supporting members so as to be capable of adjusting a gap between the screw mounting members, and an operating knob which is supported on an operating end of the adjusting screw so as to be switchable between a first position where the operating knob extends substantially in parallel to an axial direction of the adjusting screw and a second position where the operating knob extends in a direction substantially perpendicular to the axial direction of the adjusting screw.

The disclosure also provides an embroidery frame which holds a workpiece cloth, comprising an outer frame formed into a substantially annular shape and having a discontinuity formed by partially breaking the annularity of the outer frame so that the outer frame has two ends located opposite each other with the discontinuity being interposed therebetween, an inner frame configured to be fitted with an inner periphery of the outer frame so that the workpiece cloth is held between the outer and inner frames, a clamping mechanism which clamps the outer frame against the inner frame and includes a pair of screw-supporting members provided on the ends of the outer frame respectively and an adjusting screw which is mounted on the screw-supporting members so as to be capable of adjusting a gap between the screw mounting members, an operating shaft which rotates the adjusting screw and is provided so as to be swingable between a first location where central axes of the operating shaft and the adjusting screw extend in an identical direction or a different direction and a second location where the operating shaft is inclined in a direction such that a space between the outer frame and the operating shaft is increased, a coupling mechanism which couples the operating shaft with the adjusting screw to transmit a rotational torque of the operating shaft, and an operating knob which is supported on an operating end of the operating shaft so as to be switchable between a first position where the operating knob extends substantially in parallel to an axial direction of the operating shaft and a second position where the operating knob extends in a direction substantially perpendicular to the axial direction of the operating shaft.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a plan view of an embroidery frame according to one embodiment;

FIGS. 2A and 2B are enlarged plan views of a clamping mechanism when an operating knob assumes first and second positions respectively;

FIG. 3 is a longitudinal section of the clamping mechanism taken along line III-III in FIG. 2A;

FIG. 4 is an enlarged cross-sectional view of the clamping mechanism when the operating knob assumes the first position;

FIG. 5 is an enlarged cross-sectional view of the clamping mechanism when the operating knob assumes the second position;

FIG. 6 is a perspective view of a sewing machine with the embroidery frame being attached thereto;

FIG. 7 is a plan view of the embroidery frame according to a second embodiment;

FIG. 8 is an enlarged plan view of the clamping mechanism;

FIG. 9 is an enlarged front view of the clamping mechanism;

FIG. 10 is an enlarged front view of the clamping mechanism when the operating shaft has been swung to a second location;

FIG. 11 is an enlarged plan view of the clamping mechanism when the operating knob assumes the second position;

FIG. 12 is an enlarged front view of the clamping mechanism when the operating knob assumes the second position;

FIG. 13 is an enlarged longitudinally sectional front view of the clamping mechanism when the operating knob assumes the first position;

FIG. 14 is an enlarged cross-sectional plan view of the clamping mechanism when the operating knob assumes the first position;

FIG. 15 is an enlarged longitudinally sectional front view of the clamping mechanism when the operating shaft is located at a second position and the operating knob assumes the second position;

FIG. 16 is a plan view of a part of a coupling mechanism;

FIG. 17 is a front view of the part of the coupling mechanism; and

FIG. 18 is an exploded perspective view of the clamping mechanism.

DETAILED DESCRIPTION

A first embodiment will be described with reference to FIGS. 1 to 6. A sewing machine 1 capable of performing an embroidery sewing will first be described. Referring to FIG. 6, the sewing machine 1 includes a bed 2 extending in a right-left direction, a pillar 3 extending upward from a right end of the bed 2 and an arm 4 extending leftward from an upper end of the pillar 3. The arm 4 has a distal end serving as a head 5. The side where an operator of the sewing machine 1 is located will hereinafter be referred to as “front” and the opposite side will be referred to as “back.” The side where the pillar 3 is located will be referred to as “right” and the opposite side will be referred to as “left.”

A needle bar 6 to which a needle (not shown) is attached is mounted on the head 5 so as to be movable upward and downward. An embroidery sewing presser foot 7 is also mounted on the head 5. The bed 2 has an upper surface on which a needle plate (not shown) is mounted so as to correspond to the needle bar 6. Below the needle plate are provided a rotary hook which forms stitches in cooperation with the needle and a hook mechanism driving the rotary hook. In the arm 4 and the head 5 are provided a main shaft driven by a sewing machine motor, a needle bar mechanism moving the needle bar 6 upward and downward by drive of the main shaft and a needle thread take-up mechanism moving a needle thread upward and downward in synchronization with upward/downward movement of the needle bar 6.

An embroidery frame transfer device 8 is detachably attached to a left end of the bed 2. The embroidery frame transfer device 8 includes a carriage to which an embroidery frame 10 holding a workpiece cloth W is detachably attached. The embroidery frame 10 will be described in detail later. The sewing machine 1 further includes a Y-direction transfer mechanism 9 transferring the carriage (the embroidery frame 10) in the Y direction or the front-back direction, an X-direction transfer mechanism (not shown) transferring the Y-direction transfer mechanism 9 in the X direction or the right-left direction. The embroidery frame 10 is transferred in the X direction or the right-left direction and in the Y direction or the front-back direction on the bed 2.

A plurality of key switches is provided on a front surface of the arm 4. The key switches include a start/stop key 11 instructing start and stop of a sewing operation. A large vertically long display device 12 is provided on the front of the pillar 3. The display device 12 comprises a liquid crystal display with a touch panel. The operator operates the touch panel to select a desired one of a plurality of ordinary patterns and embroidery patterns or to set a mode of sewing operation.

The embroidery frame 10 according to the embodiment will now be described with reference to FIGS. 1 to 5 as well as FIG. 6. The embroidery frame 10 includes a generally annular outer frame 13, an inner frame 14 which is fitted with an inner periphery of the outer frame 13 so that the workpiece cloth W is held therebetween, and a clamping mechanism 15 which clamps the outer frame 13 against the inner frame 14. The outer frame 13 is made of, for example, a resin material and has four, that is, front, left, rear and right continuous outer frame sides 13 a to 13 d located within a horizontal plane. The outer frame 13 is formed into the shape of a rectangular frame that is slightly elongate in the front-back direction and has rounded corners. The left outer frame side 13 b has a mounting portion 16 which is formed integrally therewith so as to extend leftward. The mounting portion 16 is connected to the carriage of the embroidery frame transfer device 8. A discontinuity 17 is defined by partially breaking the annularity of the outer frame 13 so as to be located between the outer frame sides 13 a and 13 d or at a right front corner of the outer frame 13. The outer frame 13 is provided with a pair of screw-supporting members 18 and 19 which are located at both sides of the discontinuity 17 or more specifically, at both ends of the outer frame 13 located opposite each other, respectively. The screw-supporting members 18 and 19 constitute part of the clamping mechanism 15.

The inner frame 14 is also made of, for example, a resin material and has four continuous inner frame sides 14 a to 14 d formed integrally therewith and located within a horizontal plane. The inner frame 14 is formed into the shape of a generally rectangular frame and sized so as to be fitted with an inner periphery of the outer frame 13. The inner frame sides 14 a to 14 d have ribs 14 e formed integrally on inner peripheral edges respectively. The inner frame 14 is thus reinforced by the ribs 14 e in order to be prevented from deformation due to an external force.

The clamping mechanism 15 is provided with the paired screw-supporting members 18 and 19 and an adjusting screw 20 as shown in FIGS. 2A, 2B and 3 as well as in FIG. 1. The screw-supporting members 18 and 19 are formed so as to protrude outward from a right end of the outer frame side 13 a and a front end of the outer frame side 13 d, that is, in parallel right diagonally forward. The screw-supporting members 18 and 19 are opposed to each other at both sides of the discontinuity 17. The adjusting screw 20 is used to adjust a distance between the screw-supporting members 18 and 19 and extends through the screw-supporting members 18 and 19. The adjusting screw 20 is made of a metal material and has a right proximal end (an operating end side) on which an operating knob 25 is mounted as shown in FIG. 3. The adjusting screw 20 further has a larger-diameter portion 20 a located on the left of the operating knob 25 and a smaller-diameter shaft portion located on the left of the larger-diameter portion 20 a. The shaft includes a part which excludes a proximal end side (a right end side) and serves as a male screw 20 b formed with a male thread.

The screw-supporting member 18 located on the left as viewed in FIG. 3 has an insertion hole 18 a which is formed so as to extend therethrough in the right-left direction. The shaft portion of the adjusting screw 20 has a distal end which is adapted to extend through the insertion hole 18 a. Accordingly, the insertion hole 18 a has a larger diameter than an external diameter of the shaft portion. The screw-supporting member 18 has a circular hole 18 b formed in a central portion thereof so as to vertically extend therethrough as shown in FIGS. 2A and 2B. A columnar nut member 22 is inserted into the circular hole 18 b. The nut member 22 is formed with a screw hole 22 a which horizontally extends so as to be continuous to the insertion hole 18 a, as shown in FIG. 3. The adjusting screw 20 has a male thread 20 b threadingly engaging the screw hole 22 a.

The screw-supporting member 19 located in the right as viewed in FIG. 3 has a circular hole 19 c which is located in the middle thereof and vertically extends therethrough, as shown in FIG. 3. The screw-supporting member 19 further has an insertion hole 19 a which is located on the left of the circular hole 19 c and extends horizontally (in the right-left direction) and an insertion hole 19 b which is located on the right of the circular hole 19 c and extends horizontally (in the right-left direction in FIG. 3). The circular hole 19 b has a larger diameter than the insertion hole 19 a. The insertion hole 19 a has an inner diameter sufficient for the shaft portion of the adjusting screw 20 (a part having no male thread) to extend therethrough. The insertion hole 19 b has an inner diameter sufficient for the larger-diameter portion 20 a of the adjusting screw 20 to extend therethrough.

A columnar stopper 23 is fixed in the circular hole 19 c. The stopper 23 extends horizontally (in the right-left direction in FIG. 3) and has a through hole 23 a through which the shaft portion of the adjusting screw 20 is to extend. The adjusting screw 20 is inserted through the through hole 19 b, the through hole 23 a of the stopper 23, the through hole 19 a and the through hole 18 a of the screw-supporting member 18. The male thread 20 b is screwed into the screw hole 22 a of the nut member 22. In this case, the adjusting screw 20 is positioned relative to the screw-supporting member 19 so that the larger-diameter portion 20 a of the adjusting screw 20 abuts the stopper 23. A spring serving as a biasing member is fitted between the screw-supporting members 18 and 19 in such a manner that a gap is defined around the male thread 20 b of the adjusting screw 20. The screw-supporting members 18 and 19 are biased by an elastic force of the spring 21 in such respective directions that the screw-supporting members 18 and 19 depart from each other or that the distance therebetween is increased.

When the adjusting screw 20 is turned clockwise, the male thread 20 b is screwed into the screw hole 22 a of the nut member relative to the adjusting screw 20 such that the screw-supporting member 18 is moved so as to come closer to the screw-supporting member 19, whereupon the inner peripheral surface of the outer frame 13 is clamped in such a direction that an inner diameter of the outer frame 13 is reduced. When the adjusting screw 20 is turned counterclockwise, the male thread 20 b is moved in such a direction that the male thread 20 b is relatively dropped out of the screw hole 22 a of the nut member 22, whereby the screw-supporting member 18 is moved so as to depart from the screw-supporting member 19. In this case, an elastic force of the spring 21 increases the distance between the screw-supporting members 18 and 19. In other words, since the inner peripheral surface of the outer frame 13 is rendered larger, the clamping force against the inner frame 14 is reduced. The operating knob 25 is provided on the proximal end of the adjusting screw 20. In the embodiment, the operating knob 25 is switchable between a first position (see FIGS. 2A and 4) where the operating knob 25 extends in substantially the same direction as the axial direction of the adjusting screw 20 and a second position (see FIGS. 2B and 5) where the operating knob 25 extends in the direction perpendicular to the axial direction of the adjusting screw 20.

The operating knob 25 and its circumjacent structure will now be described with reference to FIGS. 4 and 5 as well as FIG. 1. The adjusting screw 20 has a flat plate-shaped portion 24 formed integrally with the proximal end thereof adjacent to the larger-diameter portion 20 a. The flat plate-shaped portion 24 is horizontally flat as shown in FIG. 3. The operating knob 25 is mounted to the flat plate-shaped portion 24. The operating knob 25 is made of a metal material and formed into the shape of a circular column (or a rounded bar) elongate in the right-left direction as viewed in FIG. 3. The operating knob 25 includes two lengthwise ends each formed into a convex semispherical shape and a knurled portion 25 a (see FIGS. 2A and 2B) provided in an outer peripheral surface excluding both ends thereof. The operating knob 25 has a cutout groove 26 which is formed substantially in a partial central part thereof as shown in FIGS. 4 and 5. The cutout groove 26 has a first wall 26 a formed on the longer side and a second wall 26 b formed on the shorter side. The cutout groove 26 has a width such that the flat plate-shaped portion 24 of the adjusting screw 20 is insertable thereinto.

The operating knob 25 has a stepped hole 27 which is formed substantially in the lengthwise middle thereof so as to vertically extend through the operating knob 25 and so as to be generally perpendicular to the cutout groove 26 as shown in FIG. 3. A stepped screw 28 serving as a shaft member is inserted into the stepped hole 27. The flat plate-shaped portion 24 has a threaded hole 24 a which is formed at the distal end side so as to correspond to the stepped hole 27 as shown in FIGS. 4 and 5. The stepped hole 27 includes a stepped portion 27 a, a larger diameter portion located higher than the cutout groove 26 and an intermediate diameter portion located higher than the cutout groove 26, as shown in FIG. 3. A stepped screw 28 corresponds to the stepped hole 27 and the screw hole 24 a of the flat plate-shaped portion 24 and has a distal end (a lower end in FIG. 3) formed into a smaller diameter portion. The stepped screw 28 also has a middle portion formed into a threaded portion 28 b which is engageable with the screw portion 28 b, an intermediate diameter portion and an upper end formed into a head 28 a which is accommodated in the upper portion or the larger diameter portion of the stepped portion 27 a. The head 28 a of the stepped screw 28 is formed with a slot into which a flat-blade screwdriver (not shown) is inserted to be driven so that the stepped screw 28 is fixed to the flat plate-shaped portion 24.

When the operating knob 25 is mounted to the flat plate-shaped portion 24 of the adjusting screw 20, the flat plate-shaped portion 24 is inserted into the cutout groove 26. The stepped screw 28 is inserted into the stepped hole 27 from above as shown in FIG. 3 after the stepped hole 27 has been aligned with the screw hole 24 a. The threaded portion 28 b of the stepped screw 28 is then threadingly engaged with the threaded hole 24 a of the flat plate-shaped portion 24 thereby to be fixed in position. The operating knob 25 is then rotatably supported on the flat plate-shaped portion 24. In this case, an annular wave spring 29 serving as a retaining member is attached in a compressed state between the head 28 a of the stepped screw 28 and the stepped portion 27 a of the stepped hole 27.

The operating knob 25 is switchable (pivotable) between the first and second positions as described above. When the operating knob 25 assumes the first position as shown in FIGS. 2A and 4, one side of the flat plate-shaped portion 24 abuts the first wall 26 a such that the operating knob 25 extends substantially in the same direction as the axial direction of the adjusting screw 20. When the operating knob 25 assumes the second position as shown in FIGS. 2B and 5, another side of the flat plate-shaped portion 24 abuts the second wall 26 b such that the operating knob 25 extends in the direction perpendicular to the axial direction of the adjusting screw 20. Thus, the operating knob 25 is configured to pivot about 90°. When the operating knob 25 assumes the second position, the adjusting screw 20 of the flat plate-shaped portion 24 and the operating knob 25 are arranged substantially into a T-shape. With the switching in the position of the operating knob 25, the flat plate-shaped portion 24 and the cutout groove 26 pivot relative to each other. Since the wave spring 29 is attached in the compressed state, a resistive force of friction is imparted to the operating knob 25 when the operating knob 25 is caused to pivot. The operating knob 25 is thus retained in the first or second position by the resistive force of friction.

The embroidery frame 10 as constructed above will work as follows. When the workpiece cloth W is to be set on the embroidery frame 10, the operator firstly places the outer frame 13 on a work table (not shown) as shown in FIG. 1. In this case, the operating knob 25 is retained in the first position, and the distance between the screw-supporting members 18 and 19 is maintained in an increased state to some extent. The operating knob 25 is located slightly above the underside of the outer frame 13 when assuming the first position, as shown in FIG. 3. Accordingly, the operating knob 25 is prevented from contact with the work table. The operator next puts the workpiece cloth W on the upper side of the outer frame 13 while aligning the workpiece cloth W with the outer frame 13. More specifically, the operator puts the workpiece cloth W on the outer frame 13 so that an embroidery pattern to be sewn is located substantially at the center of the outer frame 13. The operator presses the workpiece cloth W downward from above while aligning the inner frame 14 so that the inner frame 14 is fitted with the inner periphery of the outer frame 13. The inner frame 14 is fitted with the inner periphery of the outer frame 13 such that the workpiece cloth W is pressed into the inner peripheral side of the outer frame 13, whereupon the workpiece cloth W is held between the inner periphery of the outer frame 13 and the outer periphery of the inner frame 14.

The operator then brings the embroidery frame 10 slightly upward and grips the operating knob 25 with his/her fingertips to turn the operating knob 25 clockwise (in the direction of arrow B in FIG. 2B). As a result, the adjusting screw 20 is turned clockwise such that screw-supporting members 18 and 19 are moved so that the distance therebetween is reduced or narrowed. The outer frame 13 can be clamped against the inner frame 14 in the above-described manner. However, since the outer diameter of the operating knob 25 is small when the operating knob 25 assumes the first position, the operator has a difficulty in turning the operating knob 25 with a sufficiently large force. Hence, the operator causes the operating knob 25 to pivot about the stepped screw 28 about 90° in the direction of arrow A shown in FIGS. 2A and 4. As a result, the operating knob 25 is switched from the first position as shown in FIGS. 2A and 4 to the second position as shown in FIGS. 2B and 5. The operator turns the operating knob 25 clockwise at his/her fingertips after having switched the operating knob 25 into the second position. When the operating knob 25 assumes the second position, the outer diameter of the operating knob 25 is increased. Accordingly, the torque for turning the adjusting screw 20 can be increased even though an operating force which turns the operating knob 25 is small. As a result, the operator can easily turn the operating knob 25 and accordingly the adjusting screw 20 with a small operating force, whereupon the outer frame 13 can be tightly clamped against the inner frame 14. The operator then plucks the outer edge (not shown) of the workpiece cloth W outward to tighten the workpiece cloth W.

After the outer frame 13 has been clamped, the operator causes the operating knob 25 to pivot to return the operating knob 25 from the second position to the first position. Subsequently, the operator attaches the embroidery frame 10 holding the workpiece cloth W to the carriage of the embroidery frame transfer device 8 for execution of an embroidery sewing operation. Since the operating knob 25 assumes the first position in this case, the operating knob 25 can be prevented from contact with the bed 2 during the sewing of an embroidery pattern.

Upon completion of the embroidery sewing operation, the operator detaches the embroidery frame 10 from the embroidery frame transfer device 8, further detaching the workpiece cloth W from the embroidery frame 10. In detachment of the workpiece cloth W, the operating knob 25 is turned counterclockwise so that the distance between the screw-supporting member 18 and 19 is increased. As a result, the clamping force the outer frame 13 imparts to the inner frame 14 is reduced such that the inner frame 14 can be detached from the outer frame 13. In this case, too, the operator can easily turn the adjusting screw 20 with a small operating force when the operator switches the operating knob 25 to the second position.

According to the above-described embroidery frame 10, the clamping mechanism 15 clamping the outer frame 13 against the inner frame 14 includes the operating knob 25 which is mounted on the proximal end of the adjusting screw 20 so as to be switchable between the first and second positions. Since the operating knob's assuming the second position is equivalent to increasing the outer diameter of the operating knob 25, the torque turning the adjusting screw 20 can be increased even though the operating force to turn the operating knob 25 is small. Accordingly, the operator can easily turn the operating knob 25 with a small operating force to tightly clamp the outer frame 13 against the inner frame 14. When the operating knob 25 is returned to the first position, the embroidery frame 10 can properly be transferred by the embroidery frame transfer device 8 without the operating knob 25 contacting the bed 2 during the sewing.

The stepped screw 28 and the wave spring 29 are used as a supporting structure for the adjusting screw 20. As a result, the supporting structure is simplified, and the operator can easily switch the position of the operating knob 25. The operator can easily turn the operating knob 25 since the adjusting screw 20 and the operating knob 25 are arranged substantially into the T-shape or are substantially perpendicular to each other when the operating knob 25 assumes the second position. In this case, the operating knob 25 can be retained in the first and second positions by the frictional resistive force of the wave spring 29. Consequently, the departure of the operating knob 25 from the second position can be suppressed when the operator turns the operating knob 25. The departure of the operating knob 25 from the first position can also be suppressed during the sewing.

The flat plate-shaped portion 24 located at the operation side end of the adjusting screw 20 is disposed in the cutout groove 26 of the operating knob 25 in the embodiment. Consequently, the operating knob 25 can compactly be disposed. Furthermore, the operating force applied to the operating knob 25 can reliably be transmitted to the adjusting screw 20 by a relatively simpler structure. Still furthermore, the pivot range of the operating knob 25 can be limited by the abutment of the first or second wall 26 a or 26 b of the cutout groove 26 against the flat plate-shaped portion 24. Additionally, the operating knob 25 has both lengthwise ends formed into respective convex semispherical shapes. Consequently, a good operational feeling can be obtained when the operator pinches the operating knob 25 with his/her fingertips to operate the knob.

A second embodiment will be described with reference to FIGS. 7 to 18. The second embodiment differs from the first embodiment in the construction of the clamping mechanism 35. In the second embodiment, an operating shaft 39 is provided for turning the adjusting screw 38 and the operating knob 54 is mounted on the operation side end of the operating shaft 39, instead of the direct provision of the operating knob on the proximal end of the adjusting screw. The identical or similar parts in the second embodiment are assigned with the same reference symbols as those in the first embodiment and detailed description of these parts will be eliminated. Only the difference between the first and second embodiments will be described.

The embroidery frame 30 according to the second embodiment has the outer and inner frames 31 and 32 each of which is formed substantially into a rectangular annular shape. Each frame is made of a resin material. The inner frame 32 is fitted with the inner periphery of the outer frame 31 such that the workpiece cloth W is held between the outer and inner frames 31 and 32. The outer frame 31 has four, that is, front, left, rear and right frame sides 31 a to 31 d located within a horizontal plane. The left frame side 31 b has a mounting portion 33 which is formed integrally on the middle thereof so as to extend leftward. The mounting portion 33 is to be coupled to the carriage of the embroidery frame transfer device 8. The disconnection section 34 is defined in the center of the front outer frame side 31 a so as to break continuity of the outer frame 31. The disconnection section 34 is provided with the clamping mechanism 35 for clamping the outer frame 31 against the inner frame 32. The inner frame 32 has four inner frame sides 32 a to 32 d located within a horizontal plane and ribs 32 e formed on inner peripheral edges of the inner frame sides 32 a to 32 d respectively.

The clamping mechanism 35 will now be described in detail with reference to FIGS. 8 to 18. The clamping mechanism 35 includes a pair of screw-attached portions 36 and 37, an adjusting screw 38, an operation shaft 39, a coupling mechanism 40, a pivoting mechanism 41 and an operating knob 54. The screw-attached portions 36 and 37 are formed integrally with the outer frame side 31 a so as to be located at right and left sides of the split section 34 respectively and so as to protrude frontward from the outer frame side 31 a. The screw-attached portions 36 and 37 are opposed to each other and has respective through insertion holes 36 a and 37 a extending horizontally or in the right-left direction as shown in FIG. 14. The left screw-attached portion 36 has a circular hole 36 b extending vertically. A columnar nut member 42 is inserted into the circular hole 36 b. The nut member 42 is formed with a screw hole 42 a which extends in the right-left direction so as to continue to the insertion hole 36 a.

The adjusting screw 38 includes a head 38 a located at the proximal end (a right end as viewed in FIG. 14) thereof, a shaft 38 b extending leftward from the head 38 a and a male thread 38 c located at the distal end side. The distal end of the adjusting screw 38 is inserted through the insertion holes 37 a and 36 a in turn from the right to be threadingly engaged with the male thread 38 c of the screw hole 42 a of the nut member 42. The head 38 a is formed into the shape of a cylinder with a right open end and is located on the right outer wall of the screw attachment portion 37. The shaft 38 b is inserted through the insertion hole 37 a thereby to be rotatably supported. A pair of washers 43 and 44 and a stop ring 45 are fitted with the shaft 38 b so as to abut the right and left outer walls of the screw attachment portion 37 respectively. When the adjusting screw 38 is turned clockwise, the paired screw attachment portions 36 and 37 are moved such that the distance therebetween is narrowed or reduced. When the adjusting screw 38 is turned counterclockwise, the screw attachment portions 36 and 37 are moved such that the space therebetween is expanded or increased.

The following will describe a coupling mechanism 40 which transfers rotary torque of the operating shaft 39 to the adjusting screw 38. The head 38 a of the adjusting screw 38 is formed with a coupling hole 46 having an open end (a right end as viewed in FIGS. 13 and 14). The open end of the coupling hole 46 is formed into an inverse tapered shape with the right opening side having a larger diameter. The coupling hole 46 has an inner peripheral wall formed with a pair of slits 47 (see FIGS. 17 and 18) extending axially with respect to the adjusting screw 38. The operating shaft 39 has a distal end 39 a having a smaller diameter than the coupling hole 46 thereby to be inserted into the coupling hole 46 with a space being defined therebetween. An engagement pin 48 is inserted through a hole formed in the distal end 39 a so as to be slidable and so as to be perpendicular to the central axis as shown in FIG. 16 as well as in FIG. 14. The engagement pin 48 has both ends slidably engaged with the slits 47 respectively such that the operating shaft 39 is coupled to the adjusting screw 38.

The operating shaft 39 is turnable about the shaft center, and the torque is transmitted from the distal end 39 a of the operating shaft 39 via the engagement pin 48 to the head 38 a of the adjusting screw 38. Since the distal end 39 a of the operating shaft 39 is slidably in engagement with the slits 47, the engagement pin 48 is rotatable or swingable about the engagement pin 48 relative to the head 38 a. Thus, the coupling mechanism 40 functions as a universal joint which is capable of transmitting the rotary torque to the adjusting screw 38 even when the operating shaft 39 is turned to be inclined at any inclination. A cylindrical cover sleeve 49 (see FIG. 18) made of a resin is attached to the head 38 a of the adjusting screw 38 in order that the engagement pin 48 may be prevented from dropping off the distal end 39 a of the operating shaft 39.

A pivotably supporting mechanism 41 shown in FIGS. 11 and 14 pivotably supports the operating shaft 39 on the outer frame 31. The operating shaft 39 is further mounted on the adjusting screw 38 so to be swingable about the shaft center of the adjusting screw 38 via the coupling mechanism 40 and the pivotably supporting mechanism 41. The operating shaft 39 is swingable between a first location (the location as shown in FIG. 9) where the shaft centers of the operating shaft 39 and the adjusting screw 38 are directed in the same direction and a second location (the location as shown in FIG. 10) where the gap between the operating shaft 39 and the outer frame 31 is rendered larger or increased. The first location may be determined such that the shaft centers of the operating shaft 39 and the adjusting screw 38 are slightly displaced from each other.

A pivotably supporting hardware 50 is fixed closely to the underside of the outer frame 31 by a pair of screws 51 as shown in FIGS. 8, 11, 14 and 18. The pivotably supporting hardware 50 includes a base 50 a, a pivotably supporting portion 50 b and a stopper 50 c. The base 50 a is fixed to the outer frame 31 (the right screw attachment portion 37) by a screw 51, and the pivotably supporting portion 50 b rises vertically from the base 50 a. The stopper 50 c protrudes from an end of the base 50 a thereby to limit a swinging range of the operating shaft 39.

A coupler 52 made of a resin is fitted with an outer periphery of the shaft 39 b of the operating shaft 39 as shown in FIGS. 13 and 15. The generally semicylindrical coupler 52 has a centrally located coupling hole 52 a into which the operating shaft 39 is inserted. The coupler 52 is prevented by a stepped portion 39 c and a stop ring 55 from being axially moved relative to the operating shaft 39. The operating shaft 39 is rotatably inserted through the coupler 52. The operating shaft 39 is supported by a support arm 56. The operating shaft 39 has a flat plate-shaped portion 53 formed integrally on the right proximal end thereof as viewed in FIG. 13 (an operation side end). An operating knob is attached to the flat plate-shaped portion 53. The operating knob 54 will be described in detail later.

The support arm 56 is formed from a bent metal plate. The operation side end of the support arm 56 is inserted into an inner groove (see FIG. 18) of the coupler 52 to be fixed via a rectangular plate-shaped washer 57 by a screw 58. The other end of the support arm 56 is pivotably supported on the pivotably supporting portion 50 b of the hardware 50 by a stepped pin 59 so as to be in parallel to the central axis of the adjusting screw 38. The central axis of the adjusting screw 58 is perpendicular to a central axis of the adjusting screw 38.

The operating shaft 39 is pivotable about the stepped pin 59. The operating shaft 39 is swingable between a first location (as shown in FIG. 9) where the operating shaft 39 assumes a horizontal position and a second location (as shown in FIG. 10) where the operating shaft 39 is upwardly inclined. The operating shaft 39 assuming the horizontal position is in parallel to the outer frame side 31 a. When the operating shaft 39 assumes the second location, a clearance between the outer frame 31 and the operating shaft 39 and a clearance between the a horizontal plane inclusive of the underside of the inner frame 32 and the operating shaft 39 are increased.

A wave spring (not shown) is attached between a head 59 a of the stepped pin 59 and the support arm 56. The wave spring applies a frictional resistance force to the operation side end of the support arm 56 when the operation side end pivots, so that the operating shaft 39 can be supported at any location which is located between a first location and a second location and includes the first and the second locations. When located at the first location, the operating shaft 39 is received from below by the stopper 50 c of the pivotably supporting hardware 50, whereupon a range of swinging movement of the operating shaft 39 is limited.

The operating knob 54 located at the proximal end of the operating shaft 39 is provided so as to be changeable between the first location and the second location in the second embodiment. When assuming the first location, the operating knob 54 extends substantially in the axial direction of the operating shaft 39 (see FIGS. 8 to 10). When assuming the second location, the operating knob 54 extends in a direction crossing the axial direction of the operating shaft 39 or a direction perpendicular to the axial direction of the operating shaft 39 in this case (see FIGS. 11 and 12).

The construction of the operating knob 54 will be described with reference to FIGS. 13 to 18 as well as to FIGS. 7 to 12. The proximal end (a portion located nearer the distal end side than the stepped portion 39 c) of the operating shaft 39 is provided with the flat plate-shaped portion 53 formed integrally therewith. The operating knob 54 is mounted on the flat plate-shaped portion 53. The operating knob 54 is made of a metal material and is formed into a columnar shape elongate in the right-left direction as viewed in FIGS. 9 and 13. the operating shaft 39 and the operating knob 54 are positioned so as to generally form a T-shape when the operating knob 54 assumes the second location. The flat plate-shaped portion 53 and the cutout groove 60 are caused to pivot relative to each other with the change in the location of the operating knob 54. In this case, since the wave spring 63 is attached in the compressed state, a frictional resistance force is imparted to the operating knob 54 by the wave spring 63. The operating knob 54 is held in the first or second location by the frictional resistance force. The operating knob 54 has a knurling 54 a (see FIGS. 9 and 10) formed on a peripheral surface thereof except for both ends. The operating knob 54 also has a cutout groove 60 which is formed in a part thereof so as to substantially extend along a central axis thereof, as shown in FIGS. 13 and 14. The cutout groove 60 has a long side first wall 60 a and a short side second wall 60 b. The cutout groove 60 has a width such that the flat plate-shaped portion 53 is insertable thereinto.

The operating knob 54 has a stepped hole 61 formed through a lengthwise central portion thereof so as to vertically extend therethrough in perpendicular to the cutout groove 60 as viewed in FIG. 14. A stepped screw 62 serving as a shaft member is inserted through the stepped hole 61. The flat plate-shaped portion 53 has a screw hole 53 a formed in the distal end side thereof so as to correspond to the stepped hole 61. The stepped hole 61 includes an intermediate diameter portion and a larger diameter portion both located below the cutout groove 60. The stepped hole 61 includes a stepped portion which is formed on the surface side so as to be adjacent to the larger diameter portion. The stepped screw 62 corresponds to the stepped hole 61 and a screw hole 53 a of the flat plate-shaped portion 53. The stepped screw 62 has a distal end formed with a smaller diameter portion, a middle portion formed with a thread portion 62 b threadingly engaged with the screw hole 53 a, and a lower side formed with a head 62 a which is adapted to be accommodated in the stepped portion 61 a. The head 62 a of the stepped screw 62 is formed with a groove into which a straight slot screwdriver is to be inserted in order that the stepped screw 62 is fixed to the flat plate-shaped portion 53.

When the operating knob 54 is to be mounted to the flat plate-shaped portion 53 of the operating shaft 39, the flat plate-shaped portion 53 is inserted into the cutout groove 60 of the operating knob 54 so that the stepped screw 61 is aligned to the screw hole 53 a. The stepped screw 62 is inserted into the stepped hole 61 from the front side as viewed in FIG. 14 (a lower part of the plane of paper), so that the thread portion 62 b of the stepped screw 62 is threadingly engaged with the thread hole 53 a of the flat plate-shaped portion 53 thereby to be fixed. As a result, the operating knob 54 is pivotably mounted on the flat plate-shaped portion 53. In this case, an annular wave spring 63 (see FIG. 18) serving as a supporting member is attached between the head 62 a of the stepped screw 62 and the stepped portion 61 a of the stepped hole 61 in a compressed state.

When the operating knob 54 assumes the first position, one side of the flat plate-shaped portion 53 abuts the first wall 60 a, thereby extending substantially in the same direction as the axial direction of the operating knob 39, as shown in FIG. 13. When the operating knob 54 assumes the second position, the opposite side of the flat plate-shaped portion 53 abuts the second wall 60 b, thereby extending in the direction crossing the axial direction of the operating knob 39, as shown in FIG. 15. The operating knob 54 is thus configured to pivot about 90°, and the operating shaft 39 and the operating knob 54 are positioned so as to form a generally T-shaped arrangement when the operating knob 54 assumes the second position. The flat plate-shaped portion 53 and the cutout groove 60 are caused to pivot relative to each other with the change in the position of the operating knob 54. In this case, since the wave spring 63 is attached in the compressed state, a frictional resistance force is imparted to the operating knob 54 by the wave spring 63. The operating knob 54 is held in the first or second position by the frictional resistance force.

The embroidery frame 30 according to the second embodiment will work as follows. When setting the workpiece cloth W to the embroidery frame 30, the operator places the outer frame 31 on a work table (not shown) as shown in FIG. 7. In this case, the operating shaft 39 is set to the first location and the operating knob 54 is set to the first position. The distance between the screw-attached portions 36 and 37 of the outer frame 31 is kept increased to some extent. When the operating shaft 39 is located at the first location and the operating knob 54 assumes the first position, the operating knob 54 is located slightly above the underside of the outer frame 31 as shown in FIG. 9. As a result, the operating knob 54 is prevented from contact to the work table. The operator then puts the workpiece cloth W onto the upper side of the outer frame 31 while aligning the workpiece cloth W to the outer frame 31. More specifically, the operator puts the workpiece cloth W on the outer frame 31 so that a part of the workplace cloth W where an embroidery patterns is to be sewn is located substantially at the center of the outer frame 31. The operator presses the upper side of the workpiece cloth W downward while aligning the inner frame 32 so that the inner frame 32 is fitted with the inner periphery of the outer frame 31. Thus, the inner frame 32 is fitted with the inner periphery such that the workpiece cloth W is pressed to the inner peripheral side of the outer frame 31 thereby to be held between the inner and outer frames 32 and 31.

Subsequently, the operator pinches the operating knob 54 with his/her fingertips and swings the operating shaft 39 in the direction of arrow C from the first location as shown in FIG. 9 so that the operating shaft 39 occupies the second location where the distance between the operating shaft 39 and the outer frame 31 is increased, as shown in FIG. 10. Subsequently, the operator causes the operating knob 54 to pivot from the first position as shown in FIG. 10 in the direction of arrow D until the operating knob 54 assumes the second position as shown in FIGS. 11 and 12.

The operator then pinches the operating knob 54 with his/her fingertips to turn the operating knob 54 clockwise (in the direction of arrow F in FIG. 12). Turn of the operating knob 54 is transmitted via the operating shaft 39 and the coupling mechanism 40 to the adjusting screw 38, which is then turned clockwise so that the screw attachment portions 36 and 37 are moved such respective directions as to reduce the distance therebetween. As a result, the outer frame 31 can tightly be clamped against the inner frame 32. However, since the outer diameter of the operating knob 54 is small in the case where the operating knob 54 assumes the first position, it is difficult for the operator to turn the operating knob 54 with a sufficiently large force. Thereupon, the operator causes the operating knob 54 to pivot about the stepped screw 54 by 90° in the direction of arrow D in FIG. 10. As a result, the operating knob 54 is changed from the first position as shown in FIG. 10 to the second position as shown in FIG. 12.

After having switched the operating knob 54 to the second position, the operator pinches the operating knob 54 with his/her fingertips to turn the knob 54 clockwise. Since the condition where the operating knob 54 assumes the second position corresponds to the increased outer diameter of the operating knob 54, the torque turning the adjusting screw 38 can be increased even though the operating force to turn the operating knob 54 is small. Thus, the operator can easily turn the operating knob (the adjusting screw 38) with the small operating force, whereupon the outer frame 31 can tightly be clamped against the inner frame 32. In this case, the operator pulls the outer edge of the workpiece cloth W outward to eliminate slack of the workpiece cloth W.

The operator causes the operating knob 54 to pivot thereby to return the operating knob 54 from the second position to the first position after having completed the clamping of the outer frame 31. The operator then swings the operating knob 54 downward (in the direction opposite arrow C in FIG. 9) to return the operating shaft 39 from the second location to the first location. Subsequently, the operator attaches the embroidery frame 30 holding the workpiece cloth W to the carriage of the embroidery frame transfer device 8, then executing the embroidery sewing operation. Since the operating shaft 39 occupies the first location and the operating knob 54 assumes the first position, the operating knob 54 can be prevented from contacting the bed 2 during the sewing of the embroidery pattern.

Upon completion of the embroidery sewing operation, the operator detaches the embroidery frame 30 from the embroidery frame transfer device 8, further detaching the workpiece cloth W from the embroidery frame 30. In detachment of the workpiece cloth W from the embroidery frame 30, the operating knob 54 is turned counterclockwise so that the distance between the screw-attached portions 36 and 37 is increased, whereby the outer frame 31 is unclamped. As a result, the inner frame 32 can be detached from the outer frame 31. In this case, too, the operator swings the operating shaft 39 to the second location and switches the operating knob 54 to the second position to operate the operating knob 54. Consequently, the operating knob 54 or the adjusting screw 38 can easily be turned with a smaller operating force.

According to the above-described embroidery frame 30, the clamping mechanism 35 which clamps the outer frame 31 against the inner frame 32 includes the operating shaft 39 which is swingable between the first and second locations. Furthermore, the operating knob 54 provided on the proximal end of the operating shaft 39 is switchable between the first and second positions. Since the condition where the operating knob 54 assumes the second position corresponds to the increased outer diameter of the operating knob 54, the torque turning the adjusting screw 38 can be increased even though the operating force to turn the operating knob 54 is small. Thus, the operator can easily turn the operating knob 54 (the adjusting screw 38) with the small operating force, whereupon the outer frame 31 can tightly be clamped against the inner frame 32. When the operator returns the operating knob 54 to the first position and further returns the operating shaft 39 to the first position, the embroidery frame 30 can properly be transferred by the embroidery frame transfer device 8 without contact of the operating knob 54 with the bed 2 during the sewing operation.

In the embodiment, the stepped screw 62 and the wave spring 63 are used as the structure for supporting the operating knob 54 on the operating shaft 39. Accordingly, the supporting structure for the operating knob 54 is simple such that the operator can easily change the position of the operating knob 54. When the operating knob 54 assumes the second position, the operating shaft 39 and the operating knob 54 are positioned so as to form a generally T-shaped arrangement or so as to be substantially perpendicular to each other. Consequently, the operator can easily turn the operating knob 54.

The operating knob 54 is held at the first or second position by the frictional resistance force of the wave spring 63. Accordingly, when the operator turns the operating knob 54, displacement of the operating knob 54 from the second position can be suppressed, and displacement of the operating knob 54 from the first position can be suppressed.

In the embodiment, the operating knob 54 can be disposed in a compact manner since the flat plate-shaped portion 53 of the operation side end of the operating shaft 39 is disposed in the cutout groove 60 of the operating knob 54. Furthermore, the operating force of the operating knob 54 can reliably be transmitted to the adjusting screw 38 by a relatively simpler structure. When the flat plate-shaped portion 53 abuts the first or second wall 60 a or 60 b of the cutout groove 60, the range of pivotal movement of the operating knob 54 can be limited.

In the embodiment, the operating knob 54 has both lengthwise ends formed into respective convex semispherical shapes. Consequently, a good operational feeling can be obtained when the operator pinches the operating knob 25 with his/her fingers to operate the knob.

The above-described embodiments should not be restrictive but may be expanded or modified as follows. Although the embroidery frame 10 or 30 is formed into a substantially rectangular frame shape in the foregoing embodiments, the embroidery frame may be formed into a circular or elliptic shape, instead. In each foregoing embodiment, the operating knob 25 or 54 is formed with the cutout groove 26 or 64 into which the flat plate-shaped portion 24 or 53 is inserted and supported by the stepped screw 28 or 62 serving as the shaft member. However, the above-described construction may be changed into any form only if the operating knob 25 or 54 is pivotably supported on the adjusting screw 20 or the operating shaft 39. Although the operating knob 25 or 54 is pivotable about the stepped screw 28 or 62 by about 90° in the foregoing embodiments, the angle of pivoting movement may be smaller or larger than 90°.

Although the wave spring 29 or 63 is employed as the holding member in the foregoing embodiments, another structure may be employed to hold the position of the operating knob 25 or 54. For example, an engagement protrusion may be provided on an inner wall surface of the cutout groove 26 or 60, and an engagement hole may be provided in the flat plate-shaped portion 24 or 53. The position of the operating knob 25 or 54 may be held by engagement of the engagement protrusion and the engagement hole. A handicraft embroidery frame may be used instead of the embroidery frame 10 or 30 which is attached to the sewing machine 1.

The foregoing description and drawings are merely illustrative of the present disclosure and are not to be construed in a limiting sense. Various changes and modifications will become apparent to those of ordinary skill in the art. All such changes and modifications are seen to fall within the scope of the appended claims. 

1. An embroidery frame which holds a workpiece cloth, comprising: an outer frame formed into a substantially annular shape and having a discontinuity formed by partially breaking the annularity of the outer frame so that the outer frame has two ends located opposite each other with the discontinuity being interposed therebetween; an inner frame configured to be fitted with an inner periphery of the outer frame so that the workpiece cloth is held between the outer and inner frames; a clamping mechanism which clamps the outer frame against the inner frame and includes a pair of screw-supporting members provided on the ends of the outer frame respectively and an adjusting screw which is mounted on the screw-supporting members so as to be capable of adjusting a gap between the screw mounting members; and an operating knob which is supported on an operating end of the adjusting screw so as to be switchable between a first position where the operating knob extends substantially in parallel to an axial direction of the adjusting screw and a second position where the operating knob extends in a direction substantially perpendicular to the axial direction of the adjusting screw.
 2. The embroidery frame according to claim 1, wherein the operating knob has a lengthwise middle portion which is rotatably mounted on a shaft member so as to be pivotable relative to the adjusting screw, and the adjusting screw and the operating knob are located so as to form a general T-shape when the operating knob assumes the second position.
 3. The embroidery frame according to claim 1, further comprising a retaining member which retains the operating knob in each of the first and second positions.
 4. The embroidery frame according to claim 2, further comprising a retaining member which retains the operating knob in each of the first and second positions.
 5. The embroidery frame according to claim 2, wherein: the operating knob has a cutout groove which is formed in a part thereof so as to extend in the lengthwise direction; the operating end of the adjusting screw is provided with a generally flat plate-shaped portion which is inserted into the cutout groove; the shaft member is disposed so as to extend through the flat plate-shaped portion; and the flat plate-shaped portion and the cutout groove are caused to pivot relative to each other with switch in the position of the operating knob.
 6. The embroidery frame according to claim 4, wherein: the operating knob has a cutout groove which is formed in a part thereof so as to extend in the lengthwise direction; the operating end of the adjusting screw is provided with a generally flat plate-shaped portion which is inserted into the cutout groove; the shaft member is disposed so as to extend through the flat plate-shaped portion; and the flat plate-shaped portion and the cutout groove are caused to pivot relative to each other with change in the position of the operating knob.
 7. The embroidery frame according to claim 1, wherein the operating knob has two lengthwise ends each of which is formed into a convex semispherical shape.
 8. An embroidery frame which holds a workpiece cloth, comprising: an outer frame formed into a substantially annular shape and having a discontinuity formed by partially breaking the annularity of the outer frame so that the outer frame has two ends located opposite each other with the discontinuity being interposed therebetween; an inner frame configured to be fitted with an inner periphery of the outer frame so that the workpiece cloth is held between the outer and inner frames; a clamping mechanism which clamps the outer frame against the inner frame and includes a pair of screw-supporting members provided on the ends of the outer frame respectively and an adjusting screw which is mounted on the screw-supporting members so as to be capable of adjusting a gap between the screw mounting members; an operating shaft which rotates the adjusting screw and is provided so as to be swingable between a first location where central axes of the operating shaft and the adjusting screw extend in an identical direction or a different direction and a second location where the operating shaft is inclined in a direction such that a gap between the outer frame and the operating shaft is increased; a coupling mechanism which couples the operating shaft with the adjusting screw to transmit a rotational torque of the operating shaft; and an operating knob which is supported on an operating end of the operating shaft so as to be switchable between a first position where the operating knob extends substantially in parallel to an axial direction of the operating shaft and a second position where the operating knob extends in a direction substantially perpendicular to the axial direction of the operating shaft.
 9. The embroidery frame according to claim 8, wherein the operating knob has a lengthwise middle portion which is rotatably mounted on a shaft member so as to be pivotable relative to the operating shaft, and the operating shaft and the operating knob are located so as to form a general T-shape when the operating knob assumes the second position.
 10. The embroidery frame according to claim 8, further comprising a retaining member which retains the operating knob in each of the first and second positions.
 11. The embroidery frame according to claim 9, further comprising a retaining member which retains the operating knob in each of the first and second positions.
 12. The embroidery frame according to claim 9, wherein: the operating knob has a cutout groove which is formed in a part thereof so as to extend in the lengthwise direction; the operating end of the operating shaft is provided with a generally flat plate-shaped portion which is inserted into the cutout groove; the shaft member is disposed so as to extend through the flat plate-shaped portion; and the flat plate-shaped portion and the cutout groove are caused to pivot relative to each other with switch in the position of the operating knob.
 13. The embroidery frame according to claim 11, wherein: the operating knob has a cutout groove which is formed in a part thereof so as to extend in the lengthwise direction; the operating end of the operating shaft is provided with a generally flat plate-shaped portion which is inserted into the cutout groove; the shaft member is disposed so as to extend through the flat plate-shaped portion; and the flat plate-shaped portion and the cutout groove are caused to pivot relative to each other with switch in the position of the operating knob.
 14. The embroidery frame according to claim 8, wherein the operating knob has both lengthwise ends each formed into a generally convex semispherical shape. 